I'm very confused by the electrical setup of my 1965-built home.
Around a year ago, a home inspector told me that electrical projects
would be more costly/confusing as the house was built with a "12-volt
electrical system".

The switches are odd as I've looked at the back of a few switches and
they have 3 contacts each. one black/one red and one white. The wire
is stranded 18 or 20 gauge. When you turn any of the switches off or
on, you hear an audible "buzz" which is louder in a few rooms in the
house.

Otherwise, all of my outlets are 120 volt normal outlets, the ceiling
fans and lights are the usual solid 16 gauge romex, it's just the
switches that are odd.

I would like to replace these switches over time with modern two
position 120 volt switches so I can use dimmers, etc. Any advise on
what I should be searching for as to information about this '12 volt
system"?

-Jason